actionoptics
Well-Known Member
I'm planning on fitting a fridge and seen one which says it uses 0.25 kw /24 hours. Can someone explain or point me to a web site which explains how to convert that to amps, please?
12 volt fridge
- Thread starter actionoptics
- Start date
Talbot
Well-Known Member
1 kilowatt = 1000 watts
0.25 kilowatts = 250 watts in 24 hrs = 10.42 watts/hr
watts = volts*amps at 12v , 10.42 watts = 0.87 amps /hr
Thats the maths. I find it very difficult to believe that somebody can achieve this.
The best I have neard of is 2.5 amps/hr , thats with an installation that cost abt £1000. 6" of insulation, a top quality Danfoss compressor and a keel cooler. even then it was only achieved because of the low duty cycle due to the thickness of insulation.
I may be cynical, but expect that they got the decimal point in the wrong place!
0.25 kilowatts = 250 watts in 24 hrs = 10.42 watts/hr
watts = volts*amps at 12v , 10.42 watts = 0.87 amps /hr
Thats the maths. I find it very difficult to believe that somebody can achieve this.
The best I have neard of is 2.5 amps/hr , thats with an installation that cost abt £1000. 6" of insulation, a top quality Danfoss compressor and a keel cooler. even then it was only achieved because of the low duty cycle due to the thickness of insulation.
I may be cynical, but expect that they got the decimal point in the wrong place!
actionoptics
Well-Known Member
Thanks, Talbot. I'll contact the supplier in the morning. The model is the Shoreline R37 Chest Fridge with remote motor. The cabinet size is a 410 mm cube with an internal capacity of 37 litres so I'll now try to work out the thickness of the insulation.
Talbot
Well-Known Member
Here is some more data for you.
The smallest Danfoss compressor is the 35 see fact sheet [url="http://www.penguinfrigo.co.uk/pdfs/PARIS_35F.pdf"]http://www.penguinfrigo.co.uk/pdfs/PARIS_35F.pdf[/url][/url]
Thisis the same price just for the compressor as the model you are looking at! It is an air cooled variant (i.e.. as close to the spec that you are looking at) It consumes 35 watts/ hour which is 3 amps. with the 6" of insulation the fridge duty cycle may be as low as 30% (i.e. only on for 30% of the time). Thus 1 amp/hr
So ask them what sort of compressor, what sort of duty cycle, how thick is the insulation, what sort of insulation (if polyurethane - best insulation, but needs protection from moisture)
This danfoss system can cope with fridges up to 100 litres, and it may be that the miniscule capacity of your system is what is keeping the power requirements down.
The smallest Danfoss compressor is the 35 see fact sheet [url="http://www.penguinfrigo.co.uk/pdfs/PARIS_35F.pdf"]http://www.penguinfrigo.co.uk/pdfs/PARIS_35F.pdf[/url][/url]
Thisis the same price just for the compressor as the model you are looking at! It is an air cooled variant (i.e.. as close to the spec that you are looking at) It consumes 35 watts/ hour which is 3 amps. with the 6" of insulation the fridge duty cycle may be as low as 30% (i.e. only on for 30% of the time). Thus 1 amp/hr
So ask them what sort of compressor, what sort of duty cycle, how thick is the insulation, what sort of insulation (if polyurethane - best insulation, but needs protection from moisture)
This danfoss system can cope with fridges up to 100 litres, and it may be that the miniscule capacity of your system is what is keeping the power requirements down.
duncan
Well-Known Member
38.5mm
William_H
Well-Known Member
Talbot has explained the maths. However the current that results is an average over 1hr period. The actual current the compressors uses is not easily discernable because it depends on how long the compressor is running for in that hour. So if the ambient temp was near 0 then the compressor would run very little, if at all, so current consumption (amp hours) over the hour is very low. But if the ambient is high , you put warm things in the fridge or the insulation is poor the current used in an hour (Amp hours) becomes very high. However the current used when the compressor is running is still the same. Expect about 8 to 10 amps or possibly less.
Your question probably relates to how long you can run the fridge from your battery without recharging or how much solar panels you need. The answer is... only experience will tell, however if is a decent fridge with reasonable insulation in warm weather expect about 30 to 50% on time.
The manufacturers claims are probably exagerated because there are so many variables form real use.
If it has a Danfoss compressor and decent insulation it is probably as good as you will get. Just make sure it is a compressor type not those electronic Peltier device types. (often described as heating and cooling).
By the way the last 2 summers a local Oz car accessory chain has imported Chinese 12 volt fridge/freezers that draw 10 amps. They were half price of comparable ones with danfoss compressor but work well. If ever you see them in UK don't dismiss as junk. This company put I thnk their own name on them so brand name is no help.
olewill
Your question probably relates to how long you can run the fridge from your battery without recharging or how much solar panels you need. The answer is... only experience will tell, however if is a decent fridge with reasonable insulation in warm weather expect about 30 to 50% on time.
The manufacturers claims are probably exagerated because there are so many variables form real use.
If it has a Danfoss compressor and decent insulation it is probably as good as you will get. Just make sure it is a compressor type not those electronic Peltier device types. (often described as heating and cooling).
By the way the last 2 summers a local Oz car accessory chain has imported Chinese 12 volt fridge/freezers that draw 10 amps. They were half price of comparable ones with danfoss compressor but work well. If ever you see them in UK don't dismiss as junk. This company put I thnk their own name on them so brand name is no help.
olewill
Andrew_Fanner
Well-Known Member
Shoreline fridges work very well and don't scoff battery. Well, for the last six years anyway, since I bought the RR14. Its been sufficiently worthwhile that I have transferred the fridge between boats. Ice after a few hours and cold beer too, what more could you ask?
Worth considering fitting an auxilliary fan if the fridge sits somewhere that can get hot, such as the cockpit. The fan uses less current than the compressor and cools the works. The fridge has connections to support this so its expected by the manufacturers. The company are very helpful if you have a query.
Worth considering fitting an auxilliary fan if the fridge sits somewhere that can get hot, such as the cockpit. The fan uses less current than the compressor and cools the works. The fridge has connections to support this so its expected by the manufacturers. The company are very helpful if you have a query.
DaCostaGreene
Well-Known Member
Rivers & creeks
Well-Known Member
Was it a fridge or a 12v coolbox designed to look like a fridge? They use much less power than a compressor based fridge. There are downsides - they take much longer to get things cold and work best when keeping things cold that have already been chilled. Don't dismiss them though because they make the beer nice and chilly and keep fresh food pretty fresh (and cost about £80 for a decent capacity).
pappaecho
Well-Known Member
I was interested in a Danfoss compressor system in a local swindlery today.
It had compressor, refrigeration plate and heat exchanger, and was good for 40-80 litres of refrigeration space.
At 6 degrees celcius, it used 1.3 amps assuming the outside ambient air temp was 22 degree C. Its max draw was 2.7 amps.
My current Peltier system uses 60 watts eg 5 amps, and is only about 15 litres.
The system costs £197 + VAT.
So I get 3 times the space to store beer, and it draws half the amount that the Peltier system does, and once down to temperature it draws 1/4 the amps.
Not bad!
It had compressor, refrigeration plate and heat exchanger, and was good for 40-80 litres of refrigeration space.
At 6 degrees celcius, it used 1.3 amps assuming the outside ambient air temp was 22 degree C. Its max draw was 2.7 amps.
My current Peltier system uses 60 watts eg 5 amps, and is only about 15 litres.
The system costs £197 + VAT.
So I get 3 times the space to store beer, and it draws half the amount that the Peltier system does, and once down to temperature it draws 1/4 the amps.
Not bad!
TrailerSailer
Well-Known Member
Which swinderly was that in? Am interested in a larger fridge for the summer hols this year.
charles_reed
Well-Known Member
Sounds like an ASU or Waeco
both use the Danfoss compressor and a solid-state inverter.
I've had one fitted since 1991, the first, using freon 12 was better than the current one
If it is either of those the figures are so optimistic as to be a misrepresentation under the terms of the Trade Descriptions Act.
Mine, running in a reasonably insulated (more than 80mm closed cell foam) 72l box uses 5 amps on supercool (when there is more than 13.6V in the system) and 4 amps in economy mode.
In an ambient of 30C it uses 45ah in 24 hours and at 38C 65ah.
Even in the UK summer 22C is pretty cold and 6C is too warm for drinkable beer - on normal eco running it keeps below 4C (the holding plate is colder than this) and goes down to a holding plate temperature of -18C, which can freeze weak beer in the coldest part of the box, on long motoring runs.
both use the Danfoss compressor and a solid-state inverter.
I've had one fitted since 1991, the first, using freon 12 was better than the current one
If it is either of those the figures are so optimistic as to be a misrepresentation under the terms of the Trade Descriptions Act.
Mine, running in a reasonably insulated (more than 80mm closed cell foam) 72l box uses 5 amps on supercool (when there is more than 13.6V in the system) and 4 amps in economy mode.
In an ambient of 30C it uses 45ah in 24 hours and at 38C 65ah.
Even in the UK summer 22C is pretty cold and 6C is too warm for drinkable beer - on normal eco running it keeps below 4C (the holding plate is colder than this) and goes down to a holding plate temperature of -18C, which can freeze weak beer in the coldest part of the box, on long motoring runs.
Topcat47
Well-Known Member
Re: Sounds like an ASU or Waeco
I store my beer in a small locker below the waterline. I keeps it cool for free......I even keep fresh minl and butter there, athough you wouldn't want to do this for more than a day or so in the case of the milk. Of course it's "real" beer not foreign Lager so it doesn't need to be iced.
I store my beer in a small locker below the waterline. I keeps it cool for free......I even keep fresh minl and butter there, athough you wouldn't want to do this for more than a day or so in the case of the milk. Of course it's "real" beer not foreign Lager so it doesn't need to be iced.
Salty John
Well-Known Member
Re: Sounds like an ASU or Waeco
I agree. I have never found a system that used less than 60amps in a day - typically running at 5 amps, 50% of the time. For that you need good insulation. If you try to economise you just get beer that is too warm and no ice cubes.
I agree. I have never found a system that used less than 60amps in a day - typically running at 5 amps, 50% of the time. For that you need good insulation. If you try to economise you just get beer that is too warm and no ice cubes.